Bulgarian and international investigators are conducting a manhunt for several possible suspects believed to have helped a suicide bomber carry out a deadly terrorist attack on a bus filled with Israeli tourists at the airport at the Black Sea resort of Burgas, Bulgarian officials told ABC News today.

Four days after the deadly blast, investigators in Bulgaria and in several other countries are still struggling to confirm the attacker's identity.

"The key question is from what country the bomber entered Bulgaria. At the moment we do not have an answer," one official said. "But what we know now is that he was not acting alone."

The results of an autopsy today provided some new information on the bomber.

Dr. Galina Mileva, who conducted the autopsy in Burgas, told ABC News in a phone interview that a DNA profile has been given to authorities. She said "the kamikaze" was definitely not a dark-skinned Arab.

"He had white skin, blue eyes and short thick brown hair," she said. "He was a male, between 20 and 30 years old, but more analysis needs to be done to determine his exact age and height."

On Friday, Bulgarian Police began distributing a sketch of an Arab-looking suspected accomplice in hopes that the public could help them in the investigation. So far, they have not broadcast the sketch on National TV.

This suspect appears to be a different man from the one believed to have been the bomber shown in photos and airport CCTV video released by Bulgarian authorities.

Afrodita Pavlova, who together with her husband runs Afrodita Tours, said that a man with a suspicious Michigan driving license -- like the one reportedly found on the dead bomber -- twice came to their office over the course of three days trying to rent a car.

They refused to rent it to him because, she said, he did not look like the person pictured on the licence. After hearing on the news that the bomber had a fake U.S. driver's license, they contacted the authorities, she said, but told them after seeing bomber's pictures, they think this is a different man.

"He was Arab-looking with short, short hair and brown eyes," Pavlova said.

Several Bulgarian media outlets have reported suspicions that the bomber could have had accomplices who detonated the explosives by cellphone.
The Bulgarian daily Standard quoted police sources today as saying that at least two suspects were believed to have backed up or controled the suicide bomber.

Bulgaria's government has not released any new information over the weekend about its ongoing investigation. The attack occurred shortly after the Israelis boarded a bus outside the airport in Burgas, a popular tourist destination for young Israelis, about 250 miles east of capital Sofia.

Bulgarian investigators said on Friday that they had managed to obtain DNA samples from the fingers of the bomber and were checking databases in an attempt to identify him. Bulgarian Prime Minister Boiko Borisov told parliament he hoped that would be done in three to four days.

Bulgarian Interior Minister Tsvetan Tsvetanov said Friday that investigators were working round the clock to find new leads in the case, in collaboration with their counterparts from Israel and international organizations such as Interpol and Europol.

The suicide bomber was a foreigner who entered the country with fake identification documents and had been in Bulgaria for at least four days, the minister said. But authorities still don't know how he entered the country, where he came from, where he stayed or what he did while in Bulgaria.

Tsvetanov also said the blast that killed five Israeli tourists and the Bulgarian bus driver, and injured more than 30 other Israelis, was caused by three kilograms of TNT.